Portable lock systems with U-shaped shackles have grown in popularity since their conception due primarily to the level of security they provide. A category known as “U-locks” has developed particularly suited for locking bicycles and other larger items to structures, characterized generally by having a shackle substantially larger than the lock body. Other locks suitable for such uses, such as cable locks, are typically more vulnerable to thieves because they tend to rely on thinner, braided steel cables that are easier to cut through than the hardened steel shackle used in typical U-locks. However, many users nonetheless prefer cable locks to U-locks due to their versatility and price-point. Cable locks can be used in situations where a typical U-lock shackle may be too awkward or narrow to fit, such as around a telephone pole or a tree, while typical U-locks may be limited to somewhat more-specific situations, such as locking a bicycle to a bicycle rack. Despite any such disadvantages, U-locks have garnered a reputation as one of the most secure portable locks available, a reputation that can cause would-be thieves to pass by U-locked items that they may otherwise attempt to steal if they were secured with a less-secure lock such as a cable lock. Nonetheless, many users still prefer cable locks even in view of the possible lower security for the reasons mentioned above.